Note: Descriptions are shown in the official language in which they were submitted.
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MULTIVALVE CYLINDER ENGINE
The present invention relates to a multivalve
per cylinder engine. More particularly, but not
exclusively, it relates to an arrangement of valves for use
with such internal combustion engines.
It is known to provide multiple valves per
cylinder in engines. Such multiple valves can be
advantageous, especially at high speeds, since the valve
area can be increased to improve the intake and outlet
efficiencies. Alternatively or additionally, the valves
themselves may be made smaller and lighter. A common
arrangement is to have three inlet valves and two outlet
valves, the five valves being disposed equiangularly around
the cylinder head. It is of course possible to increase
the number of valves still further.
One problem with such arrangements is the means
of operating the valves. In conventional engines, the two
valves can easily be operated either by a single camshaft
or by a pair of camshafts passing above the cylinder head.
However, this is more difficult with five or more valves
and several attempts have been made to solve the problem.
One method disclosed in British patent specification no.
296125, and also in European patent specification no.
0063385 is to angle the valve stems so that all of the
inlet valves may be operated by a common cam shaft and all
of the outlet valves by another.
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However, this system, while effective for cam-
shaft purposes, raises other problems. Taking as an
example a system where there are three inlet valves
disposed on one side of the cylinder centre line, (in fact
only the centre lines of the three valves are generally on
one side of the cylinder centre line - as is common
practice in most 5-valve designs, part of some of the valve
heads will cross the cylinder centre line) it can be seen
that two valve heads are closer to the centre line than an
intermediate valve head. From the single camshaft, the
line of the centre valve must diverge from the line of the
outer valves so that they arrive at the allotted positions
in the cylinder head. It is common to employ concave domed
cylinder heads and ideally, the faces of the valve heads
should follow this domed configuration. This is impossible
with the systems disclosed in the above two patents since,
looking across the cylinder, those nearest the centre line
are more angled than is the one further from the centre
line.
It also follows that the ports closed by the
valves exit from the cylinder head at different angles.
All this makes for unnecessary complications in the design
of the cylinder head and/or piston.
It is an object of an aspect of the present
invention to provide a multivalve cylinder head design
which overcomes the above disadvantages.
An internal combustion engine in which each
cylinder thereof has a plurality of inlet ports and a
plurality of outlet ports, each port being openable and
closeable by means of a respective valve, the inlet and
outlet valves being disposed substantially on opposite
sides of a cylinder centre plane, each said valve lying
in a respective plane transverse to said centre plane
and each said valve being angled generally towards said
centre plane, said transverse planes being parallel one
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to another, there being at least three valves on a first
one of said sides, arranged with two outer valves
separated by at least one inner valve, the angle of
inclination with respect to said centre plane for said
outer valves being less than the angle of inclination
for said at least one inner valve.
All the valves may be operated indirectly by a
single camshaft through finger followers or the like.
Alternatively and preferably, the valves may be operated
directly, a separate camshaft being provided for each one
or more valves inclined at the same angle.
The separate camshafts may be connected by means
of a gearing arrangement.
The valves may each be disposed in parallel
planes transverse to said central plane.
An embodiment of the present invention will now
be more particularly described by way of example and with
reference to the accompanying drawings, in which:
FIGURE 1 is a view of a 5-valve per cylinder
combustion chamber embodying the invention;
FIGURE 2 is a cross-sectional view taken along
the line AA of Figure 1;
FIGURE 3 is a cross-sectional view of the
cylinder head taken along the line BB of Figure 1.
Referring now to the drawings, there is shown a
5-valve cylinder, and in Figures 1 and 2 outlet valves 11,
outer inlet valves 12 and central inlet valve 13 are
indicated.
Referring now to Figure 2, an outlet port 14 is
closed by an outlet valve 11, operation of which is
controlled by an outlet cam 15. Both outlet valves 11 are
disposed at the same angle of inclination ~/ to the centre
plane 16 of the cylinder and are parallel one to another.
Outer inlet ports 17 are closed by outer inlet
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valves 12, operated by outer inlet camshaft 18. Both outer
inlet valves are parallel and are inclined similarly with
respect to centre plane 16 at angle ~ 1.
Referring now to Figure 3, central inlet port 19
is closed by central inlet valve 13, operated by means of
central inlet camshaft 20. Central inlet valve 13 is
parallel to the other valves and inclined at angle ~ 2 with
respect to the central plane 16.
The various components of the valves, camshafts
and ports are generally conventional and will not be
described in more detail. A conventional spark plug 21 is
provided in a substantially central location between the
inlet and outlet valves.
As can be seen from Figures 2 and 3, the inlet
valves converge from their respective camshafts towards the
centre plane of the cylinder. Thus the faces of the inlet
valves, which are normal to the valve stems, approximate
much more closely to the desired domed configuration of the
cylinder head. In fact, by appropriate design of the
cylinder head, the ports leading thereto may all be bored
at the same angle thus facilitating the process of
construction. Furthermore, since no two adjacent valves
converge as they leave the cylinder head, there is more
room at their upper ends in which to accommodate valve
springs and tappets.
As an alternative to this multi-camshaft
arrangement, a single camshaft may be provided to operate
the various valves by means of finger followers. In
another alternative, twin camshafts are provided, one for
all the inlet valves operated via finger followers, and one
for the outlet valves.
As can be seen, the arrangement of valves allows
more room for their operating parts and allows a better
shape for the combustion chamber of the cylinder.
Construction of the cylinder head is easier since the ports
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may be bored at the same angle with respect to the cylinder
head.
The invention has been described with respect to
three inlet valves and two outlet valves. More or less of
either could of course be substituted.
